Design of Biplanar Coils for Degrading Residual Field in Magnetic Shielding Room

The uniform field and field gradient coils can be utilized for nulling the background field inside a magnetic shielding room (MSR), but the desired field produced by the coils is inevitably distorted due to the coupling effect of the magnetic shielding material. To overcome this problem, an improved method is proposed based on the image method and target field method (TFM). Directed by this method, a series of biplanar coils (BCs) are designed to produce the uniform fields and field gradients for an active compensation in an MSR. Then, their finite element models and practical experiment are established to verify the effectiveness. Compared with the conventional TFM, the proposed method shows significant effects for both uniform field coils and field gradient coils. Uniformities of the B-x and B-z increase by 79.9% and 72.5%, and the dB(x)/d(z) and dB(z)/d(z) improve by 89.6% and 63.2%, respectively. It demonstrates that this method is adopted to design the BCs fixed in MSR and holds great promise for the active compensation of environmental magnetic field in the measurement of magnetoencephalogram (MEG).